Supporting A Healthy Gut With Apples

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Introduction

There is no easy cure for the gut conditions that many of us experience, but a diet including fruit such as apples can help boost gut health, thereby improving our digestive health and our overall health.

The importance of gut health

Our gut controls the absorption of nutrients and strongly influences the immune system. Looking after your gut impacts cardiovascular health (heart and blood vessels), and research is beginning to link mental illness (e.g. depression) and neurological conditions (e.g. Alzheimer’s Disease) to gut health, too.

Can apples help?

Apples are an excellent source of Vitamin C, which is important for growing white blood cells to support our immune defences and for reducing inflammation and cell damage due to its antioxidant properties. Apples contain many polyphenols, which are effective antioxidants that can reduce inflammation in the gut, improving our digestion. Apples also contain prebiotics, which can help keep our microbiota healthy.

The ecosystem inside our guts

Our guts contain an important and diverse ecosystem of bacteria, viruses, and fungi that have a huge effect on our health. In addition to the gut microbiome, we have large populations of microbes on the skin, in the mouth, nose, reproductive organs, and other areas. It is sometimes suggested that we are more microbes than humans: the typical adult body contains around 30 trillion human cells and 38 trillion microbes. The largest microbiome in our bodies is found in our large intestine, helping us digest our food.1

Understanding the gut microbiome

We have known for many centuries that the gut contains important microflora. The idea of transplanting faecal matter to change your gut health was reported in Chinese medicine dating back to the Dong-jin dynasty (266 to 420 CE). In the 19th century, European scientists began to link gut health with emotional and psychological health - today, we call this the gut-brain axis. Recently, this has once again become a popular area of medical research. Our gut microbiome forms soon after birth but continually changes based on our diet, environment, stress and medication. Therefore, learning how to change our gut microbiome for the better could help keep us healthy.2

Balancing good and bad bacteria

Can bacteria be good and bad?

When we think of bacteria, we usually think of ‘bad’ bacteria - pathogens which can cause illness. A famous example of bad bacteria is Escherichia coli (E. coli), which causes diarrhoea and stomach cramps. Other potentially ‘bad’ bacteria include some types of Clostridium, which is common in most human guts but links to inflammation and diarrhoea, and Staphylococcus aureus, which can cause food poisoning symptoms such as vomiting.

‘Good’ bacteria are symbiotic (mutually beneficial) and work with us to carry out essential processes in our bodies. For example, Lactobacillus and Bifidobacterium can protect against negative bacterial infections in the gut, reduce inflammation to avoid issues such as IBS, and even help treat depression. Firmicutes are another type common in human intestines, which produce butyrates and help prevent a ‘leaky gut’.3, 4, 5

Prebiotics

Prebiotics are plant fibres which stimulate the growth of healthy bacteria in our guts because they reach the colon undigested (like a fertiliser, promoting healthy populations of bacteria). An example of a prebiotic fibre is pectin, found in apples.

Probiotics

Probiotics are foods or supplements containing live bacteria (and other microbes) which aim to improve the balance of ‘good’ bacteria in the gut. Probiotics include fermented foods such as yoghurt, kefir, pickles, miso, and kombucha. 

An apple a day

Apples as a fibre powerhouse

Apples are 4-5% dietary fibre, which is essential for digestion and regular, healthy bowel movements. Fibre is known to help with weight loss as well as decrease inflammation and risk of cardiovascular disease (such as heart disease). Particularly the apple skin is very high in fibre: unpeeled apples contain double the fibre, as well as increased vitamin A and potassium, relative to peeled apples.6

Pectin: a gut-boosting compound found in apples

Pectin is a prebiotic fibre found to support gut health significantly, helping to prevent both diarrhoea and constipation. Pectin helps us lower bad cholesterol (LDL), reducing the risk of heart attacks and strokes. Because our enzymes and stomach acid are unable to digest pectin, it reaches the gut intact to then be broken down by the microbiome. 

Pectin helps maintain the gut mucus layer, reducing sensitivity and helps fight pathogens in the microbiome.7, 8

Antioxidants

Apples contain many polyphenols with antioxidant properties, meaning they reduce ‘oxidative damage’ in the body, a negative process linked to ageing, cell damage, and cancer development.

 Being low-fat and high-fibre, polyphenols in apples have been shown to influence how we process fat and benefit our cholesterol levels.

Vitamin C

100 g of apple contains 4.6 mg of vitamin C - more than 10% of the NHS-recommended 40 mg per day for the average adult. Vitamin C helps us grow white blood cells to fight off infections and develop a strong immune system. It also acts as a powerful antioxidant, reducing inflammation and damage in our guts and the rest of our bodies.

Raw or cooked apples?

Raw apples contain bacteria that could be positive for re-balancing the human gut. Particularly, the fruit pulp and seeds contain high levels of bacteria that can benefit our gut health, which are partly killed by cooking.

Cooked apples are still highly nutritious, though this depends on how they are cooked. For example, boiling apples leads to vitamins leaving the fruit and entering the cooking water. One benefit is that the heat makes many polyphenols more accessible to our bodies.9

What about apple juice?

Apple juice lacks fibre but is still a good source of vitamin C and polyphenols, particularly cloudy, not-from-concentrate juice. However, you should also consider the high sugar content in apple juice.

Are apples for everyone?

Unfortunately, apples aren’t good for all guts. Apples are high in fibre and high in fructose, a sugar found in fruits, vegetables, and honey. For some people, fructose may trigger uncomfortable symptoms such as bloating, therefore apples can occasionally be a food to avoid. Furthermore, the high fibre content could be a problem for someone experiencing diarrhoea due to a condition such as IBS. When prescribed a ‘low FODMAP’ diet, apples should be avoided due to potential negative effects from the high fibre content. 

Impact on our health

Protection of gut health

An Italian study used both in vitro cells (in test tubes) and in vivo studies using rats to demonstrate that apple polyphenols protect cells in the gut against damage. Their antioxidant activity reduces the damaging inflammation in the intestines.10

Cardiovascular health

Studies have shown that eating whole apples helps cardiovascular health in several ways:

  • Decreased blood pressure.
  • Lower total cholesterol and low-density cholesterol (the bad type).
  • Reduced risk of death by heart attack.
  • Reduced risk of stroke.
  • Reduced inflammatory cytokines (which link to cell damage and cancer).
  • Apples are low in calories whilst high in fibre, aiding weight loss and helping to reduce obesity, putting individuals at a reduced risk of cardiovascular disease.11

Gut-brain connection 

It’s known that the brain and gut health are closely linked. Anxiety and stress impact gut health - think of butterflies in your stomach, nausea due to nerves, escalating to stress-triggered diarrhoea and irritable bowel syndrome (IBS). At the same time, the gut microbiome has been shown to impact neural circuits in the brain. Altering the diet to modify the microbiome species could be a potential treatment for mental illness such as depression: Kumar et al. suggest eating fish and omega-3 rich foods, prebiotics, probiotics, and potentially even faecal transplants could be utilised in depression treatment.

Dysregulated gut microbiota has also been linked to Alzheimer's and Parkinsons' due to “leaky gut” and increased inflammation. For example, studies on mice have shown that eating high-fibre diets reduces inflammation and reduces ageing effects.12,13 

Reducing cancer

Apple polyphenols seem to protect against cancer development. They directly inhibit several chemicals linked to cancer progression, which can both reduce cancer risk and improve recovery during treatment. For example, apple polyphenols inhibit growth factors and enzymes important in cell growth.14

FAQs

Are apples good for gut inflammation?

Apples are high in antioxidants, such as Vitamin A, Vitamin C, and many polyphenols, which reduce inflammation in the gut.

Are apples a good probiotic food?

Raw apples contain high levels of ‘good’ bacteria which can support our gut health, particularly the fruit pulp and the seeds, therefore this can act as a probiotic to improve our microbiome balance.

Are stewed apples good for gut health?

Stewed apples may have a reduction in healthy bacteria and vitamins relative to raw apples, but they will still be high in vitamins and other antioxidants, with some polyphenols being more available for our bodies to absorb due to the cooking process. They are also very high in fibre, which aids in gut health.

Summary

An apple a day could be hugely beneficial for a healthy gut microbiome due to its prebiotic and probiotic content, its high level of fibre, and the antioxidants and vitamins. Maintaining good gut health links to many other aspects of health, such as heart health, brain health, and cancer prevention. Include apples in your diet to reduce inflammation, improve your digestion, and, in turn, improve your overall health.

References

  1. Sender R, Fuchs S, Milo R. Revised estimates for the number of human and bacteria cells in the body. PLoS biology. 2016 Aug 19;14(8):e1002533. Available from: https://doi.org/10.1371/journal.pbio.1002533
  2. Lewandowska-Pietruszka Z, Figlerowicz M, Mazur-Melewska K. The History of the Intestinal Microbiota and the Gut-Brain Axis. Pathogens. 2022 Dec 15;11(12):1540. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9786924/
  3. Reid G, Burton J. Use of Lactobacillus to prevent infection by pathogenic bacteria. Microbes and infection. 2002 Mar 1;4(3):319-24. Available from: https://pubmed.ncbi.nlm.nih.gov/11909742/
  4. Li J, Wang J, Wang M, Zheng L, Cen Q, Wang F, Zhu L, Pang R, Zhang A. Bifidobacterium: a probiotic for the prevention and treatment of depression. Frontiers in Microbiology. 2023 May 10;14:1174800. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10205982/
  5. Okumura T, Nozu T, Ishioh M, Igarashi S, Kumei S, Ohhira M. Centrally administered butyrate improves gut barrier function, visceral sensation and septic lethality in rats. Journal of Pharmacological Sciences. 2021 Aug 1;146(4):183-91. Available from: https://pubmed.ncbi.nlm.nih.gov/34116731/
  6. Ma W, Nguyen LH, Song M, Wang DD, Franzosa EA, Cao Y, Joshi A, Drew DA, Mehta R, Ivey KL, Strate LL. Dietary fiber intake, the gut microbiome, and chronic systemic inflammation in a cohort of adult men. Genome medicine. 2021 Jun 17;13(1):102. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8212460/
  7. Chutkan R, Fahey G, Wright WL, McRorie J. Viscous versus nonviscous soluble fiber supplements: Mechanisms and evidence for fiber‐specific health benefits. Journal of the American Academy of Nurse Practitioners. 2012 Aug;24(8):476-87. Available from: https://pubmed.ncbi.nlm.nih.gov/22845031/
  8. Beukema M, Faas MM, de Vos P. The effects of different dietary fiber pectin structures on the gastrointestinal immune barrier: impact via gut microbiota and direct effects on immune cells. Experimental & Molecular Medicine. 2020 Sep;52(9):1364-76. Available from: https://www.nature.com/articles/s12276-020-0449-2
  9. Wassermann B, Müller H, Berg G. An apple a day: which bacteria do we eat with organic and conventional apples?. Frontiers in microbiology. 2019:1629. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6667679/
  10. Graziani G, D’Argenio G, Tuccillo C, Loguercio C, Ritieni A, Morisco F, Blanco CD, Fogliano V, Romano M. Apple polyphenol extracts prevent damage to human gastric epithelial cells in vitro and to rat gastric mucosa in vivo. Gut. 2005 Feb 1;54(2):193-200. Available from: https://pubmed.ncbi.nlm.nih.gov/15647180/
  11. Sandoval-Ramírez BA, Catalán Ú, Calderón-Pérez L, Companys J, Pla-Pagà L, Ludwig IA, Romero MP, Solà R. The effects and associations of whole-apple intake on diverse cardiovascular risk factors. A narrative review. Critical reviews in food science and nutrition. 2020 Dec 15;60(22):3862-75. Available from: https://pubmed.ncbi.nlm.nih.gov/31928209/
  12. Kumar A, Pramanik J, Goyal N, Chauhan D, Sivamaruthi BS, Prajapati BG, Chaiyasut C. Gut Microbiota in Anxiety and Depression: Unveiling the Relationships and Management Options. Pharmaceuticals. 2023 Apr 9;16(4):565. Available from: https://pubmed.ncbi.nlm.nih.gov/37111321/
  13. Vailati-Riboni M, Rund L, Caetano-Silva ME, Hutchinson NT, Wang SS, Soto-Díaz K, Woods JA, Steelman AJ, Johnson RW. Dietary fiber as a counterbalance to age-related microglial cell dysfunction. Frontiers in Nutrition. 2022 Mar 14;9:835824. Available from: https://pubmed.ncbi.nlm.nih.gov/35360677/
  14. Nezbedova L, McGhie T, Christensen M, Heyes J, Nasef NA, Mehta S. Onco-preventive and chemo-protective effects of apple bioactive compounds. Nutrients. 2021 Nov 11;13(11):4025. Available from: https://pubmed.ncbi.nlm.nih.gov/34836282/

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This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Elena Dennis

MSc Neuroscience University of Sussex
BSc Neuroscience, University College London

Elena is a graduate of MSc Neuroscience and an experienced teacher. Her research has included a clinical project on postural control in dystonia, and research into cellular features of motor neuron disease. She is particularly interested in neurodegenerative diseases such as Alzheimer's, Parkinson's, and progressive movement disorders. She is also interested in autoimmune conditions such as eczema, and understanding the mechanisms and treatments for cancer.

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